Step one: create a social category almost entirely out of thin air, defining arbitrarily what it is and who it applies to. For example, "white supremacist." Make up what these supposed "white supremacists" believe and what they do.

Step two: demonize the category, so that a large portion of the population at large comes to hate them, even though they've never actually encountered anyone who fits that category description.

Step three: with your grownswell of hatred against your arbitrarily created category, push through laws restricting or prohibiting that category.

Step four: apply those laws to anyone you want to suppress simply by labeling them a member of that category.